Let’s assume that:
Weight of bleaching powder = W gram
Used volume of hypo solution = V ml
Normality of hypo solution = N
The number of milli equivalents in SO-chlorine = the number of milli equivalents in iodine
= number of milli equivalents in Hypo
= N x V
Amount of chlorine = Milli equivalents x (1/1000) x Equivalent weight
= N x V x (1/1000) x 35.5
= 0.0355 x N x V
Percentage amount of chlorine available (by weight) = (0.0355 x N x V/W ) x 100